Tool
Rack heat load and airflow estimator
Every watt of IT load becomes heat that cooling must remove. This estimator converts watts to BTU per hour and cooling tons, then works out the airflow needed for a given supply and return temperature difference.
Enter your IT load below. Everything is calculated in your browser from what you type.
Your IT load
IT load
Cooling required
1.42 tons
17060 BTU/hr from 5,000 W.
- Heat output
- 5.0 kW
- BTU/hr
- 17060
- Airflow
- 1357 m³/h
- Airflow (CFM)
- 799
Assumes all electrical power becomes heat and air at sea-level density.
How this is worked out
Every input is yours to change. An estimator with hidden assumptions is not a tool.
BTU per hour is watts times 3.412. Cooling tons divide that by 12000. Airflow uses the sensible heat formula at sea-level air density, so high-altitude sites need more volume for the same heat.
The temperature difference defaults to 11 degrees C (20 F), which is typical for data centre cooling. Larger differences need less airflow.
Questions about heat load
How is BTU calculated?
BTU per hour is watts times 3.412. Every watt of IT load becomes heat. A 5000 W rack produces 17060 BTU per hour that cooling must remove.
What are cooling tons?
One ton of cooling removes 12000 BTU per hour. Divide total BTU by 12000 to get tons. A 5000 W rack needs about 1.42 tons of cooling.
How is airflow calculated?
Airflow uses the sensible heat formula at sea-level air density. Cubic metres per hour is watts times 3600 divided by air density times specific heat times temperature difference. CFM divides that by 1.699.
What temperature difference should I use?
The default is 11 degrees C (20 F), which is typical for data centre cooling. Larger differences need less airflow. High-altitude sites need more volume for the same heat.
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